#define _CRT_SECURE_NO_WARNINGS 1

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    void Inorded(TreeNode* node, vector<int>& v)
    {
        if (node == nullptr) return;
        Inorded(node->left, v);
        v.push_back(node->val);
        Inorded(node->right, v);
    }
    bool isValidBST(TreeNode* root) {
        vector<int> vec;
        Inorded(root, vec);
        for (int i = 1; i < vec.size(); i++)
        {
            if (vec[i] <= vec[i - 1]) return false;
        }
        return true;
    }
};